Grinding machine



H. E. TOWNSEND @BIND-ING MACHINE Filed oet.

May 5, 1931.

17, 1927 4 Sheets-Sheet l wm. NN

May 5, 19M., H. E. TOWNSND GRINDING MACHINE 4 Sheets-Sheet 2 Filed Oct.

May 5, l931 H. E. TowNsEND GRINDINC* MACHINE med om 1v, 1/927 4 Sheets-Sheet 5 im I . I l I y l l x I 1 l l I 1 I l x l I r .l

May 5, w31. H. E. TOWNSEND 1,803,492

GRINDING MACHINE Filed oct. 17, 1927 4 sheets-sheetl 4 Patented May 5, 193,1

UNITED NSTATES PATENT orf-ICE HERBERT E. TOWNSEND, OF EAST PROVIDENCE, RHODE ISLAND, ASSIGNOR TO BROWN AND SHARPE MANUFACTURING COMPANY, A CORPORATION OF RHODE ISLAND GBINDI'NG MACHINE Application tiled October 17, 1927. Serial No. 226,615.

the invention relates to improvements in grinding machines and more particularly to machines of that class which comprise a longitudinally movable table for supporting the Work and a grinding wheel spindle carriage for moving the grinding Wheel into and out ofcon'tact with the work. Machines of this type are provided with driving means for reciprocating the table and with means 1o for feeding the grinding wheel automatically or by hand to bring the work down to the required size. y

The primary object of this invention is to provide in a grinding machine of this description a novel and improved `cross feed mechanism for moving the grinding Wheel toward and away from the Work which is readily adapted for use in the present day commercial machine, is more completely auto- 20 matic in operation, and requires a minimum of care on the part of the operator.

`With this objectv in View, the principal feature of the invention consists in the provision in a machine of the above description '-5 of novel and improved mechanisms which act certainly and accurately when the Work has -been brought down tol size to maintain the grinding wheel in position during a predetermined period While thetable continues its reciprocatory movement to finish or polish the work, and thereafter to retract the grinding wheclfrom the work.

Another feature of the invention consists in a novel arrangement of the parts to cause i5 the cross feed, during the operation of backing the grinding Wheel away from the Work to be automatically reset so that pieces of work successively placed in the machine can be brought exactly down to size Without the i3 necessity of further adjustment by the operator. y

The several features of the invention consist also in the devices, combinations and arrangements of parts hereinafter described i5 and claimed, and together With the advantages to be obtained thereby, will be readily understood by one skilled in the art from the following description taken in A connection with the accompanying drawings, in Which 53 Fig. l is a View in right side elevation of a grinding machine embodying the-invention With parts of the cross feed mechanism shown in dotted lines; Fig. 2 is a detail view in front elevation of the mechanism for actuating the cross feed and timing mechanisms from the reciprocating table; Fig. 3 is a plan View of the parts illustrated in Fig. 2; Fig. 4 is a view in left side elevation of the parts illustrated in Fig. 2; Fig. 5 is a detail sectional view of the timing ratchet Wheel taken on the line 5-5 of Fig. 2, but with the ratchet Wheel turned to its most advanced position; Fig. 6 is a detail view in front elevation `of the timing ratchet Wheel shown in Fig. 2 with the feed paWl removed to illustrate particularly the stop pawl for holding the ratchet Wheel in advanced position; Fig. 7 is a View in rear elevation taken on tho line 7-7 of Fig. 1 illustrating particularly the mechanism for backing the grinding Wheel away from the Work; Fig. 8 is a View partly in section taken on the line 8-'8 of Fig. 7; Fig. 9 is a sectional plan view taken on the line 9 9 of Fig. 7; Fig. l() is a View in rear elevation taken on the line 10-10 o f Fig. 8 to illustrate particularly the cam and cam lever for lifting the pawls out of engagement with the ratchet Wheels; Fig. 1l is a view partly in section taken on the line 11-11 of Fig. 7 illustrating particularly the clutch lever for throwing the mechanism for backing the grinding wheel away from the Work into and out of operation; Fig. 12 is a view partly in section taken on the line 12-12 of Fig. 8 illustrating the cam and clutch lever actuated thereby for clutching the reversing shaft to the main driving shaft of the cross feed mechanism; and Fig. `13 is a detail view in rear elevation partly in section illustrating particularly a means for securing a fine adjustment of the cross feed aWl. P The grinding machine herein disclosed as the preferred embodiment of the invention is provided with the usual driving mechanism for reciprocating the table, and with a cross feed for the Wheel spindle carriage including a pawl and ratchet, which may be actuated automatically at the end of the table travel in each direction to feed the grinding Wheel toward the work. Stops of ordinary construction are provided which act to throw out the cross feed at a predetermined point and which may be set by the operator to cause the work to be brought down exactly to size. The table, however, continues to reciprocate back and forth until stopped by the operator.

With the old construction, it was necessary to back the grinding wheel away from the work manually after the work had been given a suiicient degree of polish by the continued reciprocation of the table with the cross feed out of operation, so that the machine necessarily required considerable attention as the grinding operation neared completion, and the proper finishing or polishing of the work depended entirely on the skill of the operator running the machine. In accordance with the present invention, a simple and compact mechanism is provided which is thrown into operation automatically when the work has been brought down to size and the cross feed discontinued, and acts after the lapse of a predetermined period, during which the table continues to reciprocate, to withdraw the wheel spindle carriage to its starting position.

Important features of this mechanism comprise a reversing shaft which is in alignment with the main drive shaft for the cross feed and is driven from a continuously rotating member to return the wheel spindle carriage to starting position, and a timing ratchet wheel which acts in timed relation to the reciprocation of the work supporting table after the work has been brought down to size to operatively connect the reversing shaft to the continuously rotating member to back the grinding wheel away from the work. The reversing shaft when thrown into operation, is given one complete revolution and acts first to raise the pawls to permit the timing and cross feed ratchet wheels to be turned backward to their starting positions and then is operatively clutched to the cross feed drive shaft to drive the cross feed mechanism in a reverse direction for the greater portion of one revolution of the cross feed driving shaft. The timing mechanism may be readily adjusted to vary the length of time the grinding wheel is held in advanced position so that the polishing or sizing required can be accurately measured in accordance with the requirements of the work. With the arrangement here described a more nearly automatic machine than any in present day commercial use is produced which is capable of doing work of the very highest quality and which at the same time does not requirev any close supervision on the part of the operator.

Referring more specifically to the drawings, the work supporting table of the machine is indicated at 20 and is mounted to reciprocate on ways 22 formed ori-the front part of the machine frame 24. The grinding wheel is indicated at 26 mounted on the wheel spindle carriage 28 which is adapted to move towards and away from the work on slideways 30 formed in the frame 24. During the grinding operation the grinding wheel is moved towards the work by hand or automatically by mechanism of ordinary construction which comprises the hand wheel 32 and a ratchet wheel 34. These are connected through the reduction gearing indicated at 35 and a link 36 provided with a universal joint at each end to a cross feed driving shaft 38 fixed against endwise movement in the machine frame. A worm 39 is formed on the shaft 38 which meshes with a worm wheel 40 mounted in the lower end of the vertical shaft 41 rotatably mounted in a fixed portion of the machine. The wheel spindle carriage is moved toward and away from the work through the engagement of a pinion 42 secured to the upper end of the vertical shaft 41 with a rack 43 formed on the wheel spindle carriage 28.

Vhile the automatic feed is in operation the ratchet wheel 84 is given a step by step rotation through a pawl 44 by mechanism which is actuated by the movement of the work supporting table in each direction. The pawl 44 is ad justahly secured to a pawl lever 45 which is pivotally mounted at 46 on the end of a lever 48 which is loosely mounted concentrically with the ratchet wheel 34, and is actuated to give the pawl an oscillating movement from a lever 50 and a connecting link 52. The lever 50 is pivotally mounted on the machine frame at 54 and is provided with two adjustable cam surfaces 55 which are yieldinglv pressed by a spring into contact with the V-shaped lower end of the lever 56 which is adapted at its upper end to come into contact with reversing dogs such as that indicated at 60 which are adjustably mounted on a rack 62 on the work supporting table. As the work support-ing table comes to the end of its travel in each direction, the lever 56 is rocked so that the V-shaped lower end rides over the corresponding cam 55 and depresscs thc lever 50. Cooperating with the ratchet wheel and adapted to move normally therev with is a shield 63 which is adapted to come into contact with and throw the feed pawl 44 out of operation when the work has been reduced to the desired size. This mechanism may be readily adjusted by the operator in the usual manner in accordance with the requirements of the work.

An additional adjustmen is provided between the cross feed pawl 44 and the pawl lever 45 to enable a more accurate adjustment to be made of the stop mechanism for throwing the automat-ic cross feed out of operation when the work is brought down to size. lVhen the shield 63 on the cross feed ratchet wheel 34 engages the pawl 44, the pawl will be in engagement with a particular tooth on Elli the ratchet wheel and will have advanced the ratchet wheel to a point which is determined by the throw of the pawl lever 45. If an adjustment of the shield only is relied upon to vary the point in its rotation at which the cross feed ratchet wheel is thrown out of op` eration, it is evident that this adjustment must be made for an entire tooth of the wheel. In order to determine the point at which the cross'feed ratchet wheel is thrown out of 0peration within al fraction of a tooth so that the position to which the grinding wheel is finally advanced may be determined within the closest possible limits, mechanism is provided for varying the limit of the advancing stroke of the pawl 44 through any desired fraction of a single tooth. The effect of this adjustment is to vary the position to which the ratchet wheel is advanced on each feeding stroke of the pawl lever 45. This adjustment, as illustrated in Fig. 13, comprises a screw 64 which is threaded into a nut formed on the pawl 44 and is provided with knurled head 65 so that by turning the screw the pawl is advanced or retracted longitudinally of the pawl lever 45.

After the work has been brought down to size the grinding wheel may be held in advanced position during the continued recip-v rocation of the work table to permit the tinishing or polishing of the work and then retracted to starting position by a novel and automatically acting mechanism which is thrown into operation when the cross feed is thrown out. This mechanism comprises a ratchet wheel timing device which is given a step by step rotation in timed relation to lthe reciprocation of the table Vand acts after a predetermined interval to throw into operation independently operating mechanism which drives the cross feed mechanism in a reverse direction through a predetermined distance to back the grinding wheel away from the work.

The timing mechanism comprises a ratchet wheel 66 which is rotatably mounted on the pi vot 68, and is given a step by step movement by means of a pawl 70 secured to one end of the pawl lever 72. A spring 74 coiled in a recess 76 in a disk 77 formed integrally with the hub of the ratchet wheel and secured at one end to the wheel and at the other end to a stationary disk 78 tends to turn the ratchet wheel in a direction to oppose the movement of the pawl 70. In orderto hold the ratchet wheel in the position to whichit is advanced by the pawl 70 against the pressure of the spring 74 a stop pawl 80 is provided loosely pivoted at 82 on the machine frame. The rotary7 movement of the ratchet wheel in either direction is limited by the engagement of a pin 84 secured in the ratchet wheel with a slot 86 formed in the stationary disk- 78. The pawl lever 72 is secured to alever 88 which is pivotally mounted at 90 on a fixed portion of the machine, and is given a continuous oscillating movement during the reciprocation of the table by the contact ofthe adjustable screw 92 with the cross feed lever 50.

The pawl 70 of the timing mechanism is normally held out of operation by the engagement of a cam roll 94 on the lower end of a control lever 96 with a cam surface 98 formed on the pawl lever 72. The control lever 96 is pivot-ally mounted at 100 and carries at itsupper end a lever 102 which is` mounted to swing in a. horizontal plane to engage with either of two surfaces 104 or 106 formed in a bracket 108. A spring 112 coiled about the upper end of the control lever 96 and secured at one end to the lever 102 tends to swing the' lever 102 in a direction to hold it securely in position in contact with the bracket 108, and a tension spring 114 tends to turn the control lever 96 in a direction to hold the level' 102 in contact with the surface 104 or 106. When the lever 102 is in its first or outer position in contact with the surface 104 the pawl 70 will be held out of engagement with the ratchet wheel 66 but when the lever 96 has been pushed back against the pressure of the spring 114 so that the lever 102 rests against the surface 106 the pawl 70 is permitted to drop onto the ratchet wheel. Cooperating with the lever 102 is an adjustable stop 116 which is mounted on the ratchet wheel 34 of the cross feed, and is adapted to come into contact with the lever 102 to move it against the pressure of the spring 114 from recess 104 to recess 106 to throw the pawl 70 of the timing mechanism into operation. This stop 116 is formed integrally with the bracket which' supports the shield 63 for throwing the cross feed out of operation so that by setting the shield the stop 116 will always be set at the same time to come into contact with the lever 102 at approximately the moment when the cross feed is thrown out. At the free end otthe lever 102 is formed a handle 110 so that the timing mechanism may be controlled by the operator independently ot' the mechanism above described.

The mechanism for retract-ing the griuding wheel from its advanced position is thrown into operation in timed relation to the rotation of the timing ratchet wheel 66 by means of a stop 118 which is mounted ytor adjustment in a slot 120 in a disk 'T7-mounted rigidly with the timing ratchet wheel 66 and is adapted to come into contact with a cam surface 124 formed on one arm of the lever 126.' The other arm of the lever 126 is connected by a long link 128 with one arm of a clutch control lever 130 by which the mechalnism for retracting the grinding wheel, 1o-

cated at the rear of the machine, is thrown into operation (see Figs. 7, 8, 9 and l1.) lVith this construction it will be seen that the timing mechanism may be readily adjusted within wide limits to secure a degree of polish necessary to meet the requirements of the work The mechanism for retracting the grinding wheel comprises a reversing shaft 131 which is in alignment with the cross feed driving shaft 38 and is turned through exactly one revolution first to disconnect the pawls from the cross feed and timing ratchet wheels, and thereafter to operate the cross feed mechanism in a reverse direction to retract the grinding wheel to its original position. The cross feed ratchet wheel 34 is at the same time turned backward so that this mechanism is set to receive a new piece of work without further adjustment of the shield 63. The ratchet wheel 66 of the timing device when released by the pawls 70 and 8O as hereinafter described.v snaps back under the pressure of its spring 74 to starting position where it is held by the engagement of the pin 84 with the end of the slot 86 in the disk 78.

A separate drive is provided for the reversing shaft 131 comprising a continuously rotating pulley 132 which is driven from the driving shaft 134 through a belt 136 and carries clutch teeth 138 which are adapted to engage with a corresponding sliding clutch member 140 on the clutch shaft 142. The shaft 142 also carries a gear 162 which meshes with a gear 164 on a short shaft 144 which is in turn connected by a worm 146 and a worm gear 148 to the reversing shaft 131. The clutch members 138 and 14() are normally held out of contact against the pressure of a compression spring 150, carried in a recess 1n the clutch member 146, by the engagement of a cam roll 152, formed on an arm of the clutch control lever 130, with a cam surface 154 formed in the periphery of the clutch member 140. When the clutch control lever 130 is actuated by the timing mechanism as above described, the cam roll 152 is raised from 1ts groove 154 and the clutch member 140 acting under the pressure of its spring 150 engages with the corresponding clutch member 138 of the continuously rotating pulley 132 to throw into operation the mechanism for backing the grinding wheel away from the work.

The clutch control lever 130 is held in raised position to permit the rotation of the clutch shaft 142 through a number of revolutions bv means of a cam cylinder 158 adapted to bear against a surface 160 formed on the lever 136, the number of revolutions of the. shaft 142 being limited so that tl'ie reversing shaft 131 driven through the worm 146 is made to rotate through exactly one revolution.

The cam cylinder 158 is actuated at a slow rate of speed from the shaft by means of a Geneva stop motion of ordlnary construction which is actuated through the gear 162 mounted on the shaft 142 to drive a shaft 166 on which the cam cylinder 158 is carried. To impart a. relatively slow step-by-step movement to the shaft 166, a pin 161 formed on the face of the gear 162 is adapted during each revolution of the gear to engage in one of a series of recesses 163 in a disk 165 secured to the shaft 166, and advance the disk 165 and shaft 166 through a definite angle to a point where the pin 161 again rides out of the slot. A roll 16T loosely mounted on a spring plunger 169 is adapted to engage in one of a series of corresponding recesses 171 in the disk 165 so that the shaft 166 and disk 165 are held yieldingly in position until the)v are again advanced by the continued rotation of the gear 162 with the pin 161. A t'ter one complete revolution of the ram cylinder 158, the flattened portion 168 ot the cam which corresponds to the rest position ot' the mechanism for retracting the grindingl wheel allows the clutch control lever 13 again to be brought into contact with the cam surface 154, to force the clutch member 14() back against the pressure of its springs 156 to disconnect the grinding wheel retracting mechanism from the continuously rotating pulley.r 132. The clutch shaft 142 is returned exactly to its original position by means of an indexing lever 170 which is loosely mounted on the pivot 172 of the clutch control lever '130, and carries at its upper end an indexing cam 174 adapted to engage with a correspond ing recess formed in the periphery of the clutch member 140. i

The reversing shaft 131 is connected to the shaft 38 of the cross feed by means of a sliding clutch member 176 which is keyed to slide on the reversing shaft 131 and is forced yieldingly into engagement with a corran sponding clutch surface formed on the abutting driving shaft 38 for the cross feed b v means of a compression spring 178 coiled about the reversing shaft 131 between the clutch member 176 and a fixed collar 186 on the shaft. A cam disk 182 is secured to the collar 180 and cooperates with a bell crank lever 184 which is pivotally mounted at 181i on a bracket on the machine frame and carries on one. arm a cam roll 188 to engage the cam 182. and on the other arm is provided with a yoke adapted to engage a collar loosel)Y mounted in a groove in the clutch member 176. In the rest position of the reversing shaft 131 the cam roll 188 engages a raised portion of the cam 182, thus holding the clutch member 176 out of engagement with the clutch surface on the shaft 38 against the pressure of the spring 178. lVhen the mechanism for reti-acting the grinding wheel is thrown into operation, the rotation of the cam 182 with the reversing shaft 131 causes the cam roll 188 to pass on to the low portion of the cam, thusl causing the reversing shaft to be clutched to turn with the cross feed driving shaft 38 which is driven in a reverse direction through the greater part of a revolution until the cam roll 188 again passes on to the raised portion of the cam' 182 thus disconnecting the clutch.

During the operation of the reversing mechanism as above described, to back the grinding wheel away from the work, the ratchet Wheel 34 is turned backward with the cross feed driving shaft 38 so that it is automatically reset `without further adjustment by the operator to adapt t-he machine for operation on a new piece of work. Connections are provided which are actuated from the reversing shaft 131 and act before the reyersing shaft is clutched to the cross feed driving shaft 38 to raise the feed pawl 44 out of contact with the cross feed ratchet wheel 34 while at the same time the pawls 70 and A8O are raised to permit the\timing ratchet wheel 66 to be turned back to its starting position under the influence of its vspring 74. These connections comprise a cam 190 formed on the shaft 131 and a cam lever 192 pivotally mounted at 194 on the machine and provided with a cam roll 196 adapted to engage with the cam 190. The lever 192 is connected at its free end by means of a pin and slot connection with a lever arm 198 secured to the rear en'd of a rock shaft 200 which extends through to the front of the machine, The forward end of the rock shaft 200 is provided with an arm 202 which carries a pin 204 adapted to engage with a tail on the pawl lever to disconnect the pawl from the cross feed ratchet wheel 34. `The feed pawl lever 72 and the stop pawl80v for the timing ratchet wheel are also connected to the arm 202 respectively through the links 206 and 208 which are provided at each end with pin and slot connections to permit a certain amount of play between the links and the lever arm 2 02. When the mechanism for retracting the grinding wheel is thrown into operation, the rotation of the reversing shaft 131 causes the cam roll 196 to ride onto the high portion of the cam 190 to rock the shaft 200 and arm 202 to lift the pawls out of engagement with the ratchet wheels.- The timing ratchet wheel66 snaps back to 1ts original position under the pressure of the'sprln'g 74 while the ratchet wheel 34 for the cross eed is turned back more -slowly with the wheel spindle carriage through the cross feed driving connections.

If' at the end of the operation of backing away from the grinding wheel, the operator has not stopped the reciprocation of the table, it is necessary to prevent the feed pawl 70 from dropping onto lthe timing ratchet wheel and again throwing this mechanism into operation. For this purpose a detent lever 210A is mounted on the link 206 and is held yieldingly in advanced positlon by means of a spring 212, the forward movement of the detent lever being limited by the contact of a stop 214 on the lever with the link 206.V Cooperating with the detent lever 210 is a projection 216 secured to the control lever 96. When the feed pawl 70 and link 206 are raised by the rotation of the rock shaft 200, the detent lever 210 will slide past the projection 216 moving back against the pressure of its spring 212 and will then move into position above the projection 216, thus locking the link and the feed pawl 70 against downward movement until the control lever 96 is returned to its original position.

After the machine has been set in operation by the operator, the grinding wheel .is advanced step by step at each reciprocation of the table in the usual manner until the cross feed pawl 44 is disengaged from the ratchet wheel 34 by the shield 63ste stop the advance of the grinding wheel. At the same time, the stop 116 engages the lever 102 and rotates the control lever 96 about its pivot 100 to drop the feed pawl 70 of the timing mechanism into engagement with the timing ratchet wheel 66. The timing -ratchet wheel' is now given a step by step movement during a predetermined number of reciprocations of the table until the stop 118 on the ratchet wheel 66 engages the lever 126 and acts to lift the clutch control lever 130 out of engagement with the clutch sleeve, causing the mechanism for retracting the grinding wheel from its advanced position to be clutched to the continuously rotating pulley 132. The clutch shaft 142 rotates with the pulley 132 through a number of revolutions to turn the reversing shaft 131 driven from the worm 146 through one complete revolution, wheh the clutch control lever 130 is again permitted to engage with and disconnect the clutch sleeve 140 to stop the grinding wheel rctracting mechanism.

The rotation of the reversing shaft 131 carrying the actuating cams 190 and 182 operates first to raise the pawls from the timing and cross feed ratchet wheels and then to clutch the reversing shaft 131 to the cross feed shaft 38 to rotate the cross feed shaft 38 in a reverse direction through the greater part ofv one revolution. This-movement of the cross feeddriving shaft causes the grinding wheel to bel backed away from the work a relatively large dist-ance to permit the operator readily to lace a new piece of work in the machine without danger of4 contact with the grindingwheel. The cross feed ratchet wheel 34 is turned backward through nearly two revolutions for the one turn given to the cross feed shaft 38, while the timing ratchet vsnaps back to starting position under the pressure of its spring 74.-' After placing a new piece of work in the machine, the operator advances the grinding wheel toward the work rapidly by hand rotating the Lratchet wheel 34- more than a complete revolution to bring the cross feed stop or shield 63 into operative position before setting the automatic feed in operation.

The invention having been thus described, what is claimed is:

1. A grinding machine having, lin combination, a grinding wheel mounted to move towards and away from the work, means for supporting the work, cross feed mechanism for moving the grinding wheel comprising a ratchet wheel, a pawl, a pawl carrier for actuating the pawl to rotate the ratchet wheel, means for throwing the pawl out of operation at a predetermined point in the rotation of the ratchet wheel, and means for adjusting the position of the pawl on the pawl carrier to vary the limit of the pawl feeding stroke a fraction of a tooth.

2. A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, cross feed mechanism for moving the grinding wheel comprising a ratchet wheel, a pawl actuated in timed relation to the reciprocation of thetable to impart to the ratchet wheel a step by step motion, mechanism for stopping the cross feed at a predetermined point, timing mechanism comprising a timing ratchet wheel, a pawl actuated in timed relation to the reciprocation of the table to rotate the timing ratchet wheel, and independent mechanism thrown into operation by the timing mechanism for backing the grinding wheel away from the work.

3. A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, cross feed mechanism comprising a pawl and ya ratchet wheel actuated by the reciprocation of the table for giving the grinding wheel a step by step feed towards the work, means for stopping the grinding wheel at a predetermined point, independent mechanism for reti-acting the grinding wheel from the work, and a timing mechanism comprising a pawl and a ratchctwheel actuated in timed relation to the reciprocation of the table to throw the grinding wheel retracting mechanism into operation.

4. A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel,cross feed mechanism for feeding the grinding wheel towards the work, means for automatically throwing the cross feed mechanism out of operation when the work is brought down to size, a timing mechanism comprising a pawl and a ratchet wheel rendered active in timed relation to the stopping of the cross feed mechanism, and independent mechanism thrown into operation by the timing mechanism for backing the grinding wheel away from the work.

5. A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to vthe movement of the grinding wheel, cross feed mechanism for the grinding wheel comprising a ratchet wheel, a feed pawl adapted to impart a step by step movement to the ratchet wheel, timing mechanism comprising a pawl and a ratchet wheel and independent mechanism thrown into operation by the timing mechanism acting to disengage the pawls from the ratchet wheels and thereafter to back the grinding wheel away from the work.

6. A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, cross feed mechanism for the grinding wheel comprising a pawl and a ratchet wheel, a feed lever for causing the pawl to impart a step by step movement to the ratchet wheel, means for disengaging the cross feed pawl at a predetermined point, a timing mechanism comprising a ratchet wheel, a timing pawl actuated by the feed lever, means for normally holding the timing pawl out of operation, mechanism for releasing the timing pawl when the work is brought down to size, and independent mechanism thrown into operation b the timing mechanism for backing the grinding wheel away from the work.

7. A grinding machine having, in combination,a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, a cross feed mechanism for feeding the grinding wheel towards the work comprising a pawl, a ratchet wheel and a cross feed shaft, means for stopping the feed of the grinding wheel at a predetermined point, and mechanism for backing the grinding wheel away from the work comprising a continuously moving driving pulley, a reversing shaft in alignment with the cross feed shaft, a clutch shaft in alignment with the driving pulley, a worm gear connection between the reversing shaft and the clutch shaft, means for clutching the clutch shaft to the rotating pulley, and mechanism comprising a Geneva stop motion adapted to disengage the driving pulley after a predetern'lined number of revolutions of the clutch shaft toturn the reversing shaft through one revolution.

8. A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supllt) Sti

porting table adapted to recil'irocate transversely to the movement of the grinding wheel, a crosssfeed mechanism for feeding the grinding wheel towards the work comprising a ratchet wheel, a .pawl and a cross feed shaft, means for stopping the feed of the zgrinding Wheel at a predetermined point, and mechanism for backing the grinding wheel a'way from the work comprising a continuously moving driving pulley, 'a reversing shaft through which the cross feed is driven in a reverse Vdirect-ion to hack the grinding' wheel away from the work, a clutch shaft, a worm 'connection from the clutch shaft to the reversing shaft, means for clutching the clutch shaft to the driving pulley, and means for disengaging the clutch shaft from the driving pulley Vafter a predetermined number of revolutions of the clutch shaft to turn the reversing shaft througlii one revolution.A

A grinding machine having, in combination. a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprOCate transversely to the movement of the grinding wheel, a cross feed mechanism for feeding the grinding wheel towards the work com` prising a pawl, a ratchetwheel and a cross feed shaft, means for stopping the feed of the grinding wheel at a predetermined point, and mechanism for backing the grinding wheel away from the work comprising a continuously moving driving pulley, a reversing shaft inl alignment with the cross feed shaft, a clutch for connecting the ulley to the reversing shaft, and a clutch fiir connecting the reversing shaft to the cross feed shaft to back away the grinding wheel.

l0. A grinding machine having, in combination, a grinding wheeljmounted to move towards and awa y from the Iwork, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, a cross feed mechanism for feeding the grinding wheel towards the work comprising a cross feed driving shaft, means for rotating the shaft to feed the grinding wheel towards the work, means for stopping the feed of the grinding wheel at a predetermined point, and mechanism for backing the grinding wheel away from the work oomrising a continuously movingdriving pulleya shaft in alignment withth'e'crossfeed driving shaft, a cam mounted on-the latter shaft, a clutch for connecting the two shafts actuated from the cam to connect the two shafts during a, portion ofeach revolution connecting this clutch after one revolution of the shaft. A

11. A grinding machine having, in combination. a grinding wheel mountedvto move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, a cross feed mechanism comprising'a pawl and a ratchet. wheel actuated hy the reciprocation of the table for giving the grinding wheel a step by step feed towardsV the work, a cross feed driving shaft connected thereto, mechanism for stopping the cross feed mechanism at a predetermined point, a timing mechanism, a continuously rotating driving pulley, a reversing shaft mounted in alignment with the cross feeddrivi-ng shaft, a clutch for connecting the two shafts, a cam secured to the reversing shaft for operating the clutch to connect the two shafts during a portion of each revolution of the reversing shaft, a second cam secured to the reversing shaft operating to disengage the pawl during the rotation of the reversing shaft, a clutch thrown into operation by the timing mechanism to connect the pulley to the reversing shaft, and means for rdisengaging the latter clutch after one revolution of the reversing shaft.

12. `.A grinding machine having, in combination, a grinding wheel mounted to move towards and away from the work, a work supporting table adapted to reciprocate transversely to the movement of the grinding wheel, a cross feed mechanism comprising a cross feed ratchet wheel, a feed pawl Vadapted to impart a step by step rotary movement to the ratchet wheel to feed the grinding wheel, a timing mechanism comprising a timing ratchet wheel, a feed pawl therefor, a spring adapted to resist the rotary movement of the timing ratchet wheel, a stop pawl for holding the ratchet wheel in advanced poition against the pressure of thc spring, and independent mechanism thrown into operation hy the timing mechanism acting to disengage the pawls from the two ratchet wheels to permit the timing ratchet wheel to return to its initial position under the pressure of its spring and thereafterto hack the grinding wheel away from the work.

13. A grinding machine having, in coml bination, a grinding wheel mounted to move toward and away from the work, a Work supporting table adapted to reciprocate transversely to the movement of the grinding Wheel, a cross feed mechanism comprisinged pawl anda ratchet wheel, a timing mechanism .comprising a pawl and a ratchet vwheel, means tending to hold lthe timing ratchet wheel in retracted position, means for automatically throwing the cross feed out of operation when the work is-brought of the latter shaft, a clutch forconnecting the pulley to the shaft, and means for dis-y down to size, independent mechanism thrown vvinto-operation by the timing mechanism actnation, a grinding wheel mounted to move towards and away from the work, a work Supporting table adapted to reciprocate transversely to the movement of the grinding wheel, a cross-feed mechanism comprising a` cross-feed ratchet wheel, a feed pawl adapted to impart a step by step rotary movement to the ratchet wheel to feed the grinding Wheel, a timing mechanism comprising a timing ratchet wheel, a feed pawl therefor, a spring adapted to resist the rotary movement of the timing ratchet wheel, a stop pawl for holdingr the timing ratchet wheel in advanced position against the pressure of the spring, and independent mechanism to disengage the pawls from the two ratchet wheels to return the timing ratchet wheel to its initial position under pressure of the spring and thereafter to back the grinding wheel away from the work.

In testimony whereof I have signed my name to this specification.

HERBERT E. TOVNSEND. 

